1. Field of the Invention
The present invention relates to a pressure applying device and method for using the device for treating intravascular stenosis within a blood vessel in order to restore necessary blood flow therethrough. The device includes an expandable intravascular pressure applying mechanism which is positionable in an area of surrounding intravascular stenosis within a blood vessel and operable to apply surface pressure against the inner wall of the stenotic blood vessel in order to dilate the vessel and restore it to a diameter closer to its normal diameter.
2. Description of the Prior Art
Heretofore various expandable devices have been proposed such as a so-called balloon catheter having a balloon mounted to the distal end of the catheter. The balloon is inserted into a vessel and inflated to a high pressure with the infusion of liquid. As a result once a balloon has been inflated in a vessel, flow of blood through the vessel is stopped.
Since vessels vary in thickness, a balloon catheter having a balloon of one size may require multiple balloons for one procedure. Also, the balloon itself may not be smooth when deflated and thus difficult to remove from or insert into a blood vessel.
Another system for dilating an area of intravascular stenosis includes two catheters, one slidably received over the other. In use, the smaller catheter is inserted into the vessel. Then the longer catheter is slid over the smaller catheter and, when it reaches the area of intravascular stenosis, it forces the stenotic area outwardly thereby to dilate the vessel in the area of intravascular stenosis.
Other such devices also have been proposed which have expanding splines or ribs which extend outwardly from the surface of a catheter. Examples of such previously proposed devices are disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. PATENTEE ______________________________________ 2,649,092 Wallace 3,397,699 Kahl 3,568,659 Karnegis 4,228,802 Trott 4,362,150 Lombardi, Jr. et al 4,364,392 Strother et al ______________________________________
The Wallace U.S. Pat. No. 2,649,092 discloses a catheter which is adapted to be employed in various urological procedures and which has circumferentially spaced longitudinal slots adjacent the forward end thereof. The portions of the catheter between the extremities of the slots are flexible and outwardly distortable when the forward end of the catheter is retracted with respect to the rearward end by means of a flexible member anchored to the forward end to cause such portions to exert pressure against the inner surface of a urethra in which the catheter has been inserted.
The Kahl U.S. Pat. No. 3,397,699 discloses a bladder catheter having a plurality of longitudinal slits distributed about a circumferential zone adjacent to an aperture at a distal end of the catheter. The longitudinal slits define therebetween a plurality of outwardly foldable wing elements formed when the proximal and distal ends of the circumferential zone or cylindrical envelope are drawn together by means of some resilient elastic means, such as rubber elements, located on the interior wall of the catheter and spanning the wing elements longitudinally. The catheter is adapted to receive therein a stylet which is inserted through an open proximal end of the catheter and is manipulated to draw the wing elements inward for insertion and removal of the catheter. When the catheter is positioned in a body cavity, particularly the bladder, the stylet is withdrawn allowing the wing elements to fold outwardly, retaining the expanded circumferential zone of the catheter in position.
The Karnegis U.S. Pat. No. 3,568,659 discloses an intercardiac heart pump comprising a catheter having on its extremity an expandable and contractable member. The catheter has a series of resilient, flexible ribs spaced about the catheter and parallel to the catheter's axis. One end of each rib is secured to the catheter adjacent the catheter tip, while the other end of each rib is anchored to a ring connected to a reciprocating member within the catheter which is slidably supported on the catheter. The ribs are encircled by a resilient tube which is anchored to the catheter beyond the ends of the ribs. When the reciprocating member is moved forward in the catheter, the flexible ribs are caused to bow outwardly, expanding the resilient tube which encircles the ribs. The expandable part of the catheter can be positioned within the left ventricle. When the ribs are flexed from a position generally parallel to the catheter in an outwardly bowed position, the resilient tube can be expanded to more or less fill the left ventricle.
The Trott U.S. Pat. No. 4,228,802 discloses a bladder catheter with a mechanical expanding device near the distal end thereof which can be operated by an actuator near the proximal external end thereof. The catheter comprises a pair of tubes, one within the other, forming a pair of interior lumina. The inner cylindrical lumen serves as a drainage channel and the second outer lumen formed by the cross sectional space between the two tubes provides a passage for irrigating fluids. Adjacent the distal end of the outer tube are a plurality of traversely notched splines on the inside of the outer tube extending longitudinally. parallel to the axis of the catheter. The outer tube can be moved rearward relative to the inner tube, thereby causing the splines to flex outwardly and expanding the outer tube in the area of the splines.
The outer tube is moved by means of a threaded advancing nut assembly including an annular flange formed on the proximal end of the outer tube, a screw threaded portion along the length of the inner tube, and an internally threaded nut which threadably engages the threaded portion on the inner tube and frictionally engages the annular flange on the outer tube. Rotation of the nut moves the outer tube rearwardly, flexing the splines outwardly and expanding the outer tube.
In the expanded position, the catheter is retained in position in the bladder. The inner tube also contains an auger-like spiral screw to prevent blood clots and debris from blocking the drainage.
The Lombardi, Jr., et al. U.S. Pat. No. 4,362,150 discloses an intra-aortic balloon pump attached to the end of a catheter. The proximal end of the balloon is bonded to the distal end of the catheter while the distal end of the balloon is bonded to the distal end of a rotatable tube within and extending the length of the catheter. The rotatable tube is longitudinally flexible and circumferentially rigid so that when a torque is applied to the proximal end, the torque is transmitted the length of the tube to the balloon. When the tube is rotated, the balloon is wrapped for insertion into the aorta and unwrapped for pumping, then rewrapped for removal, the balloon itself being pumped in a conventional manner via a lumen within the catheter.
The Strother et al U.S. Pat. No. 4,364,392 discloses a method and apparatus for providing therapeutic occlusions to blood vessels using an inflatable balloon mounted at the end of a catheter.
As will be described in greater detail hereinafter, the device for treating intravascular stenosis of the present invention differs from the devices previously proposed by having therein a catheter with an expandable pressure applying mechanism. The pressure applying mechanism is screw activated and provides a number of advantages, such as providing a variety of expansion sizes to accommodate varying sizes of blood vessels. An expanding mechanism that cannot burst like a balloon, and a mechanism which can be collapsed to conform closely to the diameter of the catheter to minimize trauma upon insertion and withdrawal of the device into and from a blood vessel.
Further, there is provided in the device passageways which allow the flow of blood into, through and around the expandable pressure applying mechanism for an extended period of time while the blood vessel is being dilated by the device so that the flow of blood is not interrupted.